а) (x^2-2x+1)(x^2+2x+1)=((x-1)(x+1))^2=(x^2-1)^2=x^4+1-2x^2
б) (2t-v+s)(t+2v-s)=2t^2-vt+st+4vt-2v^2+2vs-2st+vs-s^2=2t^2-2v^2-s^2+3vt-st+3vs
